Boston Celtics small forward Paul Pierce celebrates a basket against the Atlanta Hawks, Saturday in Atlanta. The Celtics won 89-81.

BOSTON — Boston Celtics coach Doc Rivers always points to the standings when asked for an assessment of his team. Whatever the record says, that’s what the Celtics are, he insists.

The record shows the Celtics are 16-17, a truly head-scratching number given their hopes and expectations entering the season. But while their record puts them in third place in the Atlantic Division and eighth in the Eastern Conference, Rivers points to another statistic he thinks is more relevant: they are 2-0 heading into Monday night’s game against the New York Knicks at Madison Square Garden, the first meeting of the season between the two teams.

That is the record the Celtics have compiled since Rivers went back to the starting lineup he envisioned all season long, a lineup that had to wait for Avery Bradley to return from off-season surgery on both shoulders. Rivers had used seven starting lineups waiting for Bradley to return and an eighth on Bradley’s first night back, a 93-83 loss last Wednesday to Memphis.

Then came “The Switch.” Brandon Bass, a starter most of last season, but underachieving in pretty much every role this season, returned to the first five, joining Paul Pierce and Kevin Garnett on the front line. Bradley joined Rajon Rondo in forming perhaps the best defensive starting backcourt in the NBA.

The results have been stunning. In their first game, the new-old starting five held the Indiana Pacers to 75 points and 32 percent shooting in a 19-point victory. Rivers called it “a substance win” but cautioned that it was only one game and just a first step.

The next night, in Atlanta, the Celtics fell behind by 19 in a first half that was more reminiscent of their underwhelming play over the first 31 games. They then held the Hawks to 28 points in the second half, nine in the third quarter, in rallying for an 89-81 victory. It represented their first winning streak in almost a month.

“It’s progress for us,” Rivers said after the Atlanta game. “We’ve played the way we wanted to six out of the last eight quarters. I look at that as progress for us defensively.”

That is critical, because the Celtics view themselves as a defensive team. In the first five years of the Garnett era, the Celtics’ defense almost always ranked in the top five in three of the vital statistical departments: fewest points allowed, defensive field-goal percentage and defensive 3-point field-goal percentage. They were No. 1 last season in both defensive field-goal percentage and defensive 3-point field-goal percentage.

This season has been another story. After the victory over the Hawks, the Celtics ranked 10th in points allowed, 18th in defensive field-goal percentage and tied for 24th in defensive 3-point field goal percentage. Throw in their usual rebounding woes (30th overall in rebounding percentage) and you had a reason that a supposedly contending team was 14-17.

The return of Bradley has been significant for a number of reasons. He is one of the best on-the-ball defenders in the league and is known for disrupting and harassing opposing point guards. He gives Rondo a target for backdoor cuts because other teams, recognizing his limited shooting range, tend to forget he is on the floor when the Celtics have the ball.

But his return also has allowed Rivers to use the newcomers Jason Terry and Courtney Lee where he has wanted to use them all season — as spark plugs off the bench. Neither player has lived up to expectations; Terry’s scoring and field-goal percentages are the lowest since his rookie year of 1999-2000, and Lee is averaging a career low in points and 3-point shooting percentage, one of his supposed strengths.

They’ve been in and out of the starting lineup as Rivers tried, without luck, to find a group that worked. Terry started 22 games (12-10), while Lee started 11 (3-8.) Their roles now are more defined. Jeff Green (who may soon be known as Mr. October because he was terrific in the preseason) has been inconsistent, but the rookie Jared Sullinger has played well, despite being a target for the officials.

Rondo, meanwhile, is coming off a triple-double (the 25th of his career) against the Hawks, while Pierce and Garnett have started every game and shown only occasional signs of senescence. Rondo leads the NBA in assists per game while Pierce is 11th in scoring. Garnett leads the team in rebounds and growls.

Pierce had 26 points against the Hawks and took it upon himself to chastise his teammates at halftime, when the Celtics trailed by 15. The team then went out and delivered a tour de force on the defensive end, a performance that once upon a time was a Celtic staple.

‘’I’m tired of seeing flashes of it for six minutes here or there, and then take six minutes off,” Pierce said, adding: “I don’t have too much left in the tank as far as my career, so this is it. I feel like the East is wide open, so there is a tremendous opportunity out there for us.”